1. Field of the Invention
Embodiments of the invention generally relate to a method and apparatus for affecting a body's core temperature. In particular, embodiments of the invention relate to elevating and/or maintaining a body's core temperature.
2. Description of the Related Art
The human body possesses a complex mechanism for regulating its core temperature. Core body temperature is the temperature of the core vital organs such as the heart, lungs, liver, and kidneys, whereas surface temperature is the temperature of the superficial skin and fat. The primary means of core temperature regulation are through specialized vascular structures called arteriovenous anastomoses (AVAs) located in the palms of the hands and the soles of the feet. AVAs are blood vessels that connect arteries and veins and act as shunts to bypass blood flow from nutritional capillary beds, such as when a body is overheating. However, in response to cold temperatures, these vascular structures will constrict, forcing blood back toward the body core. As a result, one of the symptoms people in cold conditions usually experience is coldness in their hands and feet. When an individual experiences hypothermia, blood flow to the extremities drops by nearly 90%.
As defined herein, hypothermia is a subnormal body core temperature. Hypothermia may occur when the body's temperature control mechanisms are overwhelmed by extreme external cold conditions or medically compromised such as by anesthesia. Under such conditions, the body loses more heat than it can produce and its core temperature begins to drop.
Hypothermia may be caused by exposure to extremely cold temperatures, prolonged exposure to cold temperatures, or by indirect causes such as trauma to the body or the use of an anesthetic. Anesthetics may reduce the body's ability to produce heat as well as affect the way the body regulates temperature. For example, during anesthesia, patients generally lose the ability to shiver which is one of the body's ways of generating heat. Furthermore, anesthetics reduce the body's ability to constrict blood vessels, which is one of the primary methods the body uses to conserve heat.
One way to treat hypothermia is core re-warming. In order to counter the clinical consequences of hypothermia, the vital organs must be warmed to physiological temperature. Traditional devices for treating hypothermia such as warming blankets or warm liquid baths are slow and generally ineffective in treating hypothermia. These treatments merely warm the superficial skin and fat. Since the blood flow to the extremities in hypothermic patients is severely reduced, the blood flow is incapable of efficiently conducting heat to the body's core. Current non-invasive treatments for re-warming hypothermic patients typically offer a heating rate of <1 degree Celsius per hour. Although the patient's surface temperature may increase with surface warming, the core temperature often remains low. In a post-surgical situation, this central core hypothermia can have effects on recovery and may cause post-anesthesia complications. Some advanced invasive treatments involving intravenous injection of warm fluids e.g., saline solution, are effective in quickly re-warming the body core, but require expertise and expose the patient to unnecessary risks such as infection and bleeding.
Therefore, there remains a need for an apparatus and method to adjust the body core temperature of a patient. In particular, there is a need for a non-invasive, convenient apparatus for efficiently adjusting body core temperature.